It has recently been found in this laboratory that ethanol can importantly affect meiotic chromosome behavior so that abnormalities are induced. A major goal of this project is to clarify the nature of the effects of ethanol on meiotic chromosome behavior and their implications with respect to the mechanisms of synapsis, crossing over and regular anaphase I chromosome distribution. Other recent work in this laboratory has provided new evidence of homologous chromosome pairing at the premeiotic mitosis. It is an aim of this project to assess the capacity of advance homologous association to provide the prerequisites for synapsis at meiosis and to establish preconditions for crossing over the sort which might influence the distribution of crossover sites. Approaches combine application of new techniques and laboratory findings to experimental material with an appropriate repertoire of meiotic and morphological chromosome variants. It is reasonable to expect that findings will have general applicability.